The invention relates to an unwinding apparatus for rolls of material, such as paper and paperboard rolls, which comprises a pivotable wound roll and, at each end of the roll, a pivot drive.
Unwinding apparatuses of this type are usually driven through one or more self-locking gear units, for example, worm gearing. When the drive comprises two such gear units, their inputs must be ganged or other provision must be made to secure synchronous operation of the two drives, which is complicated and expensive. Driving the gear units with two shunt-wound motors, such as induction motors, operating independently of each other entails the problem that as a result of the different characteristics of the drive motors differences in their speed of rotation will arise. While with such a drive system a rotative-speed equalization occurs through power distribution when a load is raised, lowering of the load will give rise to an increasing rotative-speed difference. The result will be uneven distribution of the torque and jamming of the gear units.